GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The accelerator pedal position (APP) sensors are mounted on the accelerator pedal/TAC module assembly. There are three individual accelerator pedal position sensors within one housing. Three separate signal, ground and reference circuits are used which are contained within the throttle actuator control (TAC) module. The APP sensor signal voltage increases as the Accelerator pedal is depressed. The signal circuits pull to ground within the TAC module.

Conditions for Running the DTC

    • DTCs P0606, P1517, P1518, P1276, P1286 are not set.
    • The ignition switch is in the crank or run position.

Conditions for Setting the DTC

APP sensor 2 disagrees with APP sensor 3 by more than 10.5 percent or the APP sensor 2 signal and APP sensor 3 signal are shorted together.

Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC

    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction free warm-up cycles.
    • The PCM receives a clear code command from the scan tool.

Diagnostic Aids

Important: :  Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

When the TAC module detects a problem within the ETC System the PCM receives a message across serial data and more than one ETC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual problem may correct more than one DTC. Keep this in mind when reviewing captured DTC info.

If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. When the TAC module detects a problem within the ETC System the PCM receives a message across serial data and more than one ETC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual problem may correct more than one DTC. Keep this in mind when reviewing captured DTC info.

DTC P1271, 72, 73 - Accelerator Pedal Position (APP) Sensor 1, 2 Correlation Error

Step

Action

Values

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Are any other DTCs set?

--

Diagnose these DTCs first

Go to Step 3

3

Replace the TAC module. Refer to Accelerator Pedal Replacement .

Did you complete the replacement?

--

Go to Step 4

--

4

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Fail Records conditions.

Does the DTC reset?

--

Go to Step 2

Go to Step 5

5

Does the scan tool indicate any DTCs set that you have not diagnosed?

--

Go to applicable DTC

System OK